Proposed studies are designed to investigate the toxicological effects of an organomercurial, such as methylmercuric hydroxide, on cells and subcellular components. It is hoped that these studies will contribute to a better understanding of the action of certain environmental pollutants at the molecular level: for instance, provide a rationale for the fact that methylmercury has been observed to cause C-mitosis as well as C-meiosis in a variety of plants, mammals and insects. Specifically, the proposed studies will be concerned: (1) with the investigation of the methylmercury-induced inhibition of mitosis in tissue cultures of mammalian cells using cytological characterization techniques with regard to chromosome variations as well as biochemical fractionation and isolation procedures in the case of subcellular components in an attempt to obtain information concerning the "target" of the action of the organomercurial, (2) with the study of the physical and chemical properties of the methylmercury complexes of chromatin and its associated histones using physico-chemical methods such as analytical ultracentrifugation, viscosity measurements, circular dichroism measurements, and other spectrophotometric techniques. The interphase chromosomes serve hereby as models of possible "target" molecules of the action of organomercurials at the molecular level. These studies constitute both a continuing and expanding effort of our current research interest. They are viewed as being a part of a long-term interest of the Principal Investigator in the physical and chemical properties as well as interrelated biological activities of biological macrmolecules in general, with a special emphasis on those properties which are subject to variation as a result of changes in the nature of the macromolecular environment.